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Mehrban ashiq Roll# 11041707-023 M.Phil Chemistry Sem 1 st

Mehrban ashiq Roll# 11041707-023 M.Phil Chemistry Sem 1 st. Assessment by GC and GC-MS of volatile hydrocarbons from biomass burning. Gunnar Barrefors and Goran Petersson. Department of Chemical Environmental Science Chalmers University of Technology

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Mehrban ashiq Roll# 11041707-023 M.Phil Chemistry Sem 1 st

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  1. Mehrbanashiq Roll# 11041707-023 M.Phil Chemistry Sem 1st

  2. Assessment by GC and GC-MS of volatilehydrocarbons from biomass burning

  3. Gunnar Barrefors and Goran Petersson Department of Chemical Environmental Science Chalmers University of Technology 412 96 Goteborg, Sweden

  4. Comparable hydrocarbon assessments were made for1:tobacco smoke 2: urban traffic emissions 3: smoke from domestic wood burning

  5. Subsequent research has focused onphenolic compounds in wood smoke

  6. Abstract Well over thirty combustion-formed non-methane hydrocarbons were determined from uncontrolled burning of biogenic materials

  7. Abstract Results are given for • straw, • conifer twigs, • newsprint and • hardwood

  8. Abstract • Samples were taken on triple-layer adsorption cartridges. • After thermal desorption, the hydrocarbons were separated by gas chromatography on an aluminium oxide column. • Samples were also taken with a gas syringe and analyzed after gas injection.

  9. Abstract • The hydrocarbon proportions were found to be remarkably similar for different kinds of biomass. • Among 21 recorded alkenes and alkadienes, ethene was predominant, • next most prominent species were propene and 1,3-butadiene. • The large proportions of ethyne and the carcinogenic benzene increased further with increasing combustion efficiency.

  10. Introduction Natural and controlled forest and grassland fires give rise to vast hydrocarbon emissions like volatile hydrocarbons, including alkenes and the carcinogenic species benzene and 1,3-butadiene which are genotoxic after metabolic biotransformation. So there is a need for analytical methods for the determination of specific organic compounds emitted from incomplete combustion of biomass.

  11. Expermental work Biomass burning: • Small-scale burning with low oxygen supply was performed in a ceramic pot. • Open burning of twigs from trees was performed on a gridiron and samples were taken nearby in the smoke plume. • Samples from a wood-stove were taken in the exit of the chimney of a remote house.

  12. Sampling • Triple-layer glass cartridges (150 mm x 4 mm i.d.) were made with separate layers of • Carbosieve S-Ill (rear layer, 0.1-0.3 g, 60-80 mesh), • Carbotrap (0.1-0.2 g, 20-40 mesh), and • Tenax TA (front layer, 0.05-0.1 g, 60-80 mesh). • The cartridges were conditioned with helium (20-40 ml min-1), initially (285°C, 60 min) and before each sampling (275°C, 10 min).

  13. Sampling • On sampling, the cartridge was connected to an air pump providing an accurate constant flow, range 10-50 ml min-. • Before and after sampling, the cartridges were kept in tight-stoppered glass tubes placed in brown bottles.

  14. Sampling volumes range less than 10 ml(pot burning) to more than 1000 ml(slightly polluted ambient air)

  15. Sampling • Duplicate samples with widely different air volumes were used to check recovery and break-through. • Single-layer Tenax cartridges were used to confirm recovery of compounds potentially sensitive to decomposition on the triple-layer cartridges. • Samples were also taken by a gas-tight syringe (50 ml) without enrichment on adsorption cartridges. This method was applied to determine methane.

  16. GC Analysis cartridges were placed in a desorption oven and connected to the carrier gas line of a gas chromatograph for desorption (235°C, 20-40 ml He min-1, 14 min) into a cold trap (5 m x 0.32 mm i.d. empty FSOT column in liquid N2). The helium gas was vented to air during desorption. Before the trap was heated (150°C, polyglycol), the vent was closed, and the carrier gas was passed through the analytical column only (30 cm s-l). Injected sample by the sampling syringe into an empty column (3.2 ml) which was then connected into the carrier gas line by gas valves. Methane passes the cold trap and is lost .

  17. GC Column • . The chromatographic separations were performed on an aluminium oxide column. • 50 m x 0.32 mm i.d. • fused silica, PLOT, • Al203/ 5% KCI,

  18. Oven temperature programming • The oven temperature program for the reported detailed separations was • 30-110°C (IO°C min-l), 110°C(isothermal, 14 min), • 11O-200°C (4°C min-l), and 200°C (isothermal).

  19. detector Flame ionization detector (FID) is used

  20. Chromatographic Separation • C2-C8 hydrocarbons emitted from biomass burning. the order of separation is alkanes < alkenes < alkadienes < alkynes • Complete determinations of all volatile hydrocarbons because other than hydrocarbons are not eluted from the Al203 column. An exception is the furans. • the alkylbenzenes elute at the maximum recommended temperature (200°C) of the column. • The temperature program was chosen to separate the carcinogenic 1,3-butadiene from pentane. • The higher elution temperature makes hydrocarbons like alkynes and alkadienes appear earlier relative to alkanes.

  21. Assessments by GC-MS • Identifications and complementary separations on a methyl silicone column were made using the capabilities of an ion trap GC-MS instrument. • Comparisons were also made with the hydrocarbons identified in vehicle polluted air and tobacco smoke

  22. Assessments by GC -MS Identifications relied on • relative retentions, • interpretations of spectra • comparisons with the NIST library of mass spectra. • The reported GC-MS separations were made using a methyl silicone column (50 m x 0.32 mm i.d. FSOT). • The linear temperature increase was 3°Cmin-l from 30°C. • The linear helium flow was 20 cmS-1. samples was injected by a gas-tight syringe (1 ml). The data interpreting speed was one mass spectrum (mlz 35-200) per second.

  23. Assessments by GC-MS The mass fragmentograms for the complex mixture of unsaturated C5 hydrocarbons were chosen to illustrate the use of GC-MS for combustion-formed compounds from biomass.

  24. Assessments by GC-MS • six isomeric acyclic pentenes, by single-ion monitoring of the mlz 70 molecular ion. • The chromatogram records furan, isoprene, the two 1,3- pentadienes, and cyclopentene, which all give rise to a prominent mlz 68 molecular ion. • The separation on the methyl silicone column complements that of the Al203 column from which 3-methyl-1- butene, cyclopentene, furan and cis-1,3-pentadiene were eluted as unresolved compound pairs.

  25. Combustion-formed compounds The stove sample from Birchwood deviates from the other three samples by more efficient and complete combustion. This results in lowered proportions of alkenes other than ethene and increased proportions of ethyne and benzene.

  26. Combustion-formed compounds Flame-less oxygen-deficient burning of glowing biomass such as wood and straw tended to give increased proportions not only of C3-C5 alkenes and alkadienes but also of C2-C5 alkanes

  27. Combustion-formed compounds • Inefficient burning of Birchwood gives rise to large proportions of furan and alkyl furans, of which 2-methylfuran is the most prominent. • The furans were recorded in varying proportions from all samples studied and are likely to be formed from • cellulose • Hemicelluloses • carbohydrates

  28. Combustion-formed compounds • The hydrocarbons from biomass burning differ markedly from urban hydrocarbon from petrol-fuelled vehicles. • A prominent portion of the pollutants in urban air consists of exhaust-emitted unburnt C4-C5 petrol hydrocarbons with large proportions of alkanes and alkylbenzenes. • On the other hand, the major combustion- formed hydrocarbons ethene, propene and ethyne are the same from biomass and petrol

  29. Combustion-formed compounds • The unbranched 1-alkenes from biomass burning. formation from lipids. • In vehicle-polluted urban air, branched isomers of C4-C6 alkenes are the most prominent. They are emitted from branched petrol alkanes and as unburnt cat cracked components of the fuel. • The carcinogenic 1,3-butadiene was a prominent component from all biomass samples, formation from cyclohexanes to be favoured . • The isoprene is very high in tobacco smoke and due to a high content of terpenoid components in tobacco. • High proportions of biomass lignin contribute to an increased formation of benzene, in a similar way as high levels of alkylbezenes in petroleum fuels . • The formation of styrene from biomass due to phenylpropane units of lignin.

  30. Results • The hydrocarbons are arranged according to • structural class • number of carbon atoms • retention order on the aluminium oxide column

  31. Results The inefficient flaming and combustion of straw is similar to that of grassland fires and open burning of agricultural and garden waste

  32. Results The open burning of twigs from spruce resembles conifer forest fires

  33. Results The hydrocarbon proportions are remarkably similar for different kinds of biomass even though the combustion conditions are quite different

  34. Results • Alkenes make half of non methane hydrocarbons • Ethene is predominent than propene and 1-butene • major diene is 1,3-butadiene • alkynes are ethyne & propyne • alkanes are ethane & propane • arenes are benzene & methylebenzene

  35. Thanks

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